Use sha2 for block hash calculation

[exeokan]

Description

Modifies HeaderWrapper::verify_hash to use accelerated sha2 crate.

Linked Issues

• Fixes use precompile for Bitcoin header hash calculation #1819

Testing

Added unit test calculate_block_hash

[exeokan]

Didn't change HeaderWrapper::block_hash and HeaderWrapper::new as they are not called from guest code, correct me if that's not the case

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.5%. Comparing base (d1d6dd4) to head (ce8b510).
Report is 6 commits behind head on nightly.

Additional details and impacted files

Files with missing lines	Coverage Δ
crates/bitcoin-da/src/spec/header.rs	83.1% <100.0%> (+7.5%)	⬆️

... and 5 files with indirect coverage changes

[kpp]

Didn't change HeaderWrapper::block_hash and HeaderWrapper::new as they are not called from guest code, correct me if that's not the case

Probably yes but tests now test your code and reflect changes